This SAE Aerospace Information Report (AIR) addresses many of the significant issues associated with effects of inlet total-pressure distortion on turbine-engine performance and stability. It provides a review of the development of techniques used to assess engine stability margins in the presence of inlet total-pressure distortion. Specific performance and stability issues that are covered by this document include total-pressure recovery and turbulence effects and steady and dynamic inlet total-pressure distortion. The intent of this document is to provide a basic understanding of the effects of inlet total-pressure distortion on the performance of gas turbine engines, particularly in military applications. In Revision D, only changes to Section 3 have been made to make the document consistent with ARP1420C and ARP6420. These changes include removing definitions inconsistent with the intent of the previously mentioned SAE Aerospace Recommended Practices (ARPs) and to add clarity to the remaining definitions. In Revision C, an introduction was incorporated to include material inadvertently omitted from Revision B. The introduction describes usages of distortion assessments during typical phases of aircraft propulsion system development and operation. Revisions to AIR1419B were made to reflect new knowledge in the following areas: Computational fluid dynamics (CFD) has become widely used for design and analysis, Highly offset inlets have imposed additional challenges, Full authority digital electronic control (FADEC) systems have become commonplace, New methods of distortion synthesis have been developed, New instrumentation techniques have been developed, New techniques for data acquisition, storage, and processing have been developed, Testing methodology/procedures have changed, and Some previously state-of-the-art techniques have become obsolete. The philosophy that was adopted to implement the changes was: Only material was added that did not exist in original document, and Dated references to “state-of-the-art,” “current technology,” etc. were revised.